fix: adjust title padding and save figure with additional padding in view_annotations

Raw Hz values with the default scientific-notation formatter produced
a cluttered "1e9" axis offset. Format ticks in MHz via a FuncFormatter
instead, matching the other spectrogram views.

src/ria_toolkit_oss/view/view_signal.py

@@ -102,13 +102,14 @@ def view_annotations(
         ]
         ax.legend(handles=legend_elements, loc="upper right", framealpha=0.2)
 
-    ax.set_title(title, fontsize=title_fontsize, pad=20)
+    ax.set_title(title, fontsize=title_fontsize, pad=14)
     ax.set_xlabel("Time (s)", fontsize=12)
-    ax.set_ylabel("Frequency (Hz)", fontsize=12)
+    ax.set_ylabel("Frequency (MHz)", fontsize=12)
+    ax.yaxis.set_major_formatter(ticker.FuncFormatter(lambda y, _: f"{y / 1e6:.1f}"))
     ax.grid(alpha=0.1)
 
     output_path, _ = set_path(output_path=output_path)
-    plt.savefig(output_path, dpi=dpi, bbox_inches="tight")
+    plt.savefig(output_path, dpi=dpi, bbox_inches="tight", pad_inches=0.2)
     plt.close(fig)
     print(f"Professional annotation plot saved to {output_path}")